Rihanna, the Barbadian queen of American dance-pop was painted in shades of a mainland rock frontwoman Saturday night, as she bounced and shimmied through a heap of pulsing, radio smashes.

But at MetLife Stadium, the sold-out crowd was never hers — she merely played groupie to the night’s indisputable star, who wore a simple, hooded sweatshirt and camo shorts.

MORE: Notes and other musings from "The Monster Tour"
Eminem, the stone-faced Detroit rapper whose razor-sharp tongue and polarizing lyrics have helped to define — or destroy, depending on your point of view — a generation of mainstream hip-hop, commanded and thrilled the leagues of fans in attendance to witness his first Garden State tour stop in 12 years.

The two-headed "Monster Tour," named for the duo’s most recent collaborative single, completed its second of three legs in East Rutherford this weekend, playing two nights sandwiched between last week’s Rose Bowl shows in Pasadena, Calif. and next week’s Comerica Park pairing in Detroit.

The show itself is a bit of a beast, topping out at 50 songs played between the two artists, who have — combined — won 20 Grammys and sold more than 250 million albums worldwide. The night included a solo set from each, as well as shared opening and closing acts. The pacing wasn’t far off from Jay-Z and Beyonce’s "On the Run" tour, which poured through MetLife in July.

Over two hours, the show explored what seems to draw Eminem and Rihanna closest — the darkk side of love, ever-present in both their songbooks. The duo’s pop and rap ultra-hit "Love the Way you Lie," which is approaching 1 billion views on YouTube, is the obvious example, with its chorus "Just gonna stand there and watch me burn / But that’s alright because I like the way it hurts."

But the jewels of the pair’s opening set were a fresher, drug-laced collab called "Numb" and a merger of Rihanna’s hit "Run this Town" and Eminem’s fierce "Renegade," which left the two at center stage, standing side-by-side as triumphant lion and lioness.

DOWN THE RABBIT HOLE

Even better may have been during Eminem’s solo set, on the rapper’s still-chilling confessional "Stan." Rihanna emerged to sing the song’s chorus, famously taken from Dido’s "Thank You." Her tone and those distinct, Caribbean inflections in her voice added something extra, and Eminem was pinpoint on the rap.

The crowd ate it up, as they did with all tracks played off Em’s 2000 breakthrough "Marshall Mathers LP," which is notoriously violent, brooding and was written through his abysmal struggle with addiction. Many fans know this, and recognize that he has cleaned up and tried to move on. His 2009 record, aptly titled "Recovery," is an easy hint. He even dedicated the album’s lead single "Not Afraid" to those battling addiction during the set.

Fans went nuts for Eminem's oldest tracks, like "The Way I Am" and "My Name Is." (Photo by Jeremy Deputat)

But those angry, unapologetic years of cursing off anyone and everyone seem to endear Eminem to much of his faithful, and they’ll take that dark trip down the rabbit hole with him if means getting to hear oldies like "Criminal" and "The Way I Am" performed live once more.

Needless to say, the MetLife audience erupted when the best-selling rapper of all time announced he was ready to revisit the old haunts. Some tracks were cut a little short, though, in favor of variety over depth. Fan favorites "The Real Slim Shady" and "My Name Is" were allotted only a verse and chorus before bleeding into something else.

Some newer songs earned the full treatment, like "Rap God," a relentless track off 2013’s "Marshall Mathers LP 2." Eminem was a bullet train on the mile-a-minute lyric, spitting his rhymes like a howitzer. The crowd cheered the speed, and he was sweating and gasping for air by the end. It was an arresting moment to see the artist, at 41, being pushed to his physical limit but still showing no signs of slowing down. His quick wit has always appeared seamless — as well as endless — and his energy on stage somehow manages to keep up.

STYLE OVER SUBSTANCE

Rihanna’s preceding set had a lot more style. A small team of dancers clothed in an all-black combo of ancient Egyptian and early ‘90s hip-hop chic surrounded the singer and ushered her through a list of bass-heavy club hits.

The crowd perked up for her most well-circulated charges, including "Umbrella" and the trancey "Where Have You Been," but glazed over during several of Rihanna’s newer, more adventurous tunes. The David Guetta-produced "Phresh Out the Runway" off 2012’s "Unapologetic," the uber-sexual "Birthday Cake" and stripper-anthem "Pour It Up," didn’t garner much of a reaction, despite the singer’s fancy hip work and choreography.

At times though, the 26-year-old diva did seem a little disinterested herself, selling the cheap sex appeal but not her commitment to the performance. Perhaps she was going through the motions on songs she’d recently played night after night on 2013’s "Diamonds World Tour." The roadshow stopped at the Prudential Center in Newark last April.

Rihanna's "Monster Tour" set was best at its most vulnerable, especially on the ballad "Stay." (Photo by Frank Micelotta)

There was redemption, however, in the set’s closing number, a popular, delicate ballad titled "Stay." For the first time this night, there was no backing track, and Rihanna’s cutting, steely voice was flawless. Vulnerability and edge replaced the singer’s showboating. Her range dazzles when it needs to, and the crowd seemed to finally connect. The tune led into "Love the Way You Lie," and afterward Eminem’s solo stuff.

The pair finished out the night together, trading the stage for a few of their top singles before closing with their most recent joint-smash "The Monster." Upon her return, Rihanna was fully engaged for "Diamonds," taking charge of the song’s wide vocal and belting out the high notes with authority. She was in full-on party mode for the dancefloor darling "We Found Love," jumping and strutting as the crowd went wild.

Eminem’s finisher was 2002’s "Lose Yourself," the rapper’s Oscar- and Grammy-winning, most successful mainstream single — to which the crowd sang every word. The rapper was as sharp on the track as the day it released, filling the lyric with all the appropriate frustration and drive.

Throughout the night, there was only one true break in his solemn persona — quoting the Will Ferrell comedy "Step Brothers," he asked the audience if they wanted to "go do karate in the garage" with him.

But of course, that’s not exactly what he said. A few four-letter words have been omitted here.